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Of Lightsails, Ramjets, and Fusion Runways

  • Paul Gilster

Abstract

Terminology is always treacherous—one field’s jargon contradicts another’s unstated assumptions—but we must now make a distinction between solar sails and lightsails. The solar sail is pushed by photons from the Sun, while the lightsail is usually much larger and driven by man-made light, microwaves, or perhaps some kind of particle beam. This distinction isn’t exclusive, though, because even before we’ve launched the first free-flying solar sail, the mission planners for The Planetary Society’s Cosmos i have plans to demonstrate both photon and microwave propulsion on the same sail. Nor is size an absolute criterion, for solar sails can be vast in their own right. The early solar sail designs NASA studied for the Halley’s Comet rendezvous reached 640,000 square meters, fully a half-mile to the side.

Keywords

Solar Wind Particle Beam Diamond Film Solar Sail Fresnel Lens 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Notes

  1. p.124
    “while centrifugal force holds the spinning, web-slung mirror taut and flat in the void.”— Eric K. Drexler, “The Canvas of the Night,” in Arthur C. Clarke, ed. Project Solar Sail (New York: Roc, 1990), 44–45.Google Scholar
  2. p.124
    “The Starflight Handbook”—Eugene Mallove and Gregory Matloff, The Starflight Handbook (New York: John Wiley & Sons, 1989). Their earlier article was “Solar Sail Starships—the Clipper Ships of the Galaxy,” Journal of the British Interplanetary Society 34 (1981), pp. 371–80.Google Scholar
  3. p.124
    “cables made of diamond to attach the payload to the sail.”—For a more recent explanation of Matloff and Mallove’s work, see Matloff’s Deep Space Probes (Chichester, U.K.: Praxis Publishing Ltd, woo).Google Scholar
  4. p.125
    “metallic foils only a few hundred atoms thick have been created.”—Eric K. Drexler, “High Performance Solar Sail Concept,” L5 News 4 (May 1979): 7-9.Google Scholar
  5. p.125
    “an ideal candidate for a mission this close to the Sun”—Mallove and Matloff, Starflight Handbook,98.Google Scholar
  6. p.126
    “and ride the laser beam all the way to the stars!”—Robert L. Forward, “Fast Forward Fifty Years,” available on the Web at www.robertforward.com/Fast_Forward_Fifty_Years.htm.Google Scholar
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    “Science Digest and Galaxy Science Fiction.”—Robert L. Forward, “Pluto, Gateway to the Stars,” Missiles and Rockets 10 (April 1962). Reprinted in Science Digest,August 1962, and later in Galaxy Science Fiction, December 1962. An indication of the continuing interest this article generated was yet another reprint, this time a revised version, in Jerry Pournelle, ed., Black Holes (New York: Fawcett Crest, 1978).Google Scholar
  8. p. 12
    : “a novel called Rocheworld in which he laid out the essential elements that would guide his later research.”—Rocheworld appeared in Analog Science Fiction/Science Fact, December 1982, and was later published in a longer version as The Flight of the Dragonfly (New York: Timescape, 1984). A final, still longer version appeared as Rocheworld in 1990 (New York: Baen Books).Google Scholar
  9. p. 127
    “a subsequent examination of the laser-driven sail concept by George Marx in Nature in 1966)..”—G. Marx, “Interstellar Vehicle Propelled by Terrestrial Laser Beam,” Nature 213 (July 1966): 22–23.Google Scholar
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    “they ignored my advice and pretended it would work.”— Forward, “Fast Forward Fifty Years.”Google Scholar
  11. p. 127
    “but now it was a deceleration that would ultimately bring them to a stop at Barnard.”— Forward, Rocheworld,144-45.Google Scholar
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    “P. C. Norem’s 1969 paper analyzing ways of stopping a laser-pushed lightsail.”— P. C. Norem, “Interstellar Travel: A Round Trip Propulsion System with Relativistic Velocity Capabilities,” American Astronomical Society paper no. 69–388, June 1969.Google Scholar
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    “whether the interstellar magnetic field was strong enough to provide the turning radius needed for the spacecraft.”—As noted in Robert L. Forward, “Roundtrip Interstellar Travel Using Laser-Pushed Lightsails,” Journal of Spacecraft and Rockets, 21 (March/April 1984):187–95. Forward himself had studied curved interstellar trajectories in a 1964 paper “Zero Thrust Velocity Vector Control for Interstellar Probes: Lorentz Force Navigation and Circling,” which ran in American Institute of Aeronautics and Astronautics Journal 2 (May 1964): 885-89.Google Scholar
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    “in the technical publication Journal of Spacecraft and Rockets in 1984.”—Forward, “Roundtrip.”Google Scholar
  15. p.129
    “is left for future generations to determine.” —Ibid., 189.Google Scholar
  16. p. 130
    “and that means the beam has to be tightly focused”—Telephone interview with Edward Belbruno, April 18, 2003.Google Scholar
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    “newer technologies that would overtake you wherever you are going.”—Telephone interview with Freeman Dyson, May 29, 2003.Google Scholar
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    “set the stage for Vostok and Apollo.”—Greg Clark, “JPL Accomplishes Laser Sail First,” space.com, March 1, 2000, at: http://www.space. com/businesstechnology/technology/laser_craft_oono 3.htmlGoogle Scholar
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    “his 1985 book The Future of Flight, written with Dean Ing.”—Leik Myrabo and Dean Ing, The Future of Flight (New York: Baen Books, 1985).Google Scholar
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    “launch prices comparable to commercial airline tickets.” —Telephone interview with Leik Myrabo, June 9, 2003.Google Scholar
  22. p.134
    “mounted in a Boeing 747–400 aircraft and used to destroy incoming missiles during their boost phase.”—“Northrop Grumman Delivers a High-Power Solid-State Laser for Missile Defense Agency’s Airborne Laser Program,” press release, Feb. 26, 2003.Google Scholar
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    “according to Myrabo, who worked on a variant of the lightcraft idea for the group.”—See Leik Myrabo et al., “Lightcraft Technology Demonstrator,” Final Technical Report, prepared under Contract No. 2073803 for Lawrence Livermore National Laboratory and the SDIO Laser Propulsion Program, June 30,1989.Google Scholar
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    “Building that space-based infrastructure is going to demand a quick way to space.” —Myrabo interview, June 9, 2003.Google Scholar
  25. p. 13
    : “by analyzing a wide range of possible substances, starting with metal sails.” —An early paper on the subject is Landis’s “Optics and Materials Considerations for a Laser-Propelled Lightsail,” presented at the 40th International Astronautical Federation Congress, Malaga, Spain, Oct. 7–12,1989 (IAA-89–664).Google Scholar
  26. p.135
    “materials like diamond, silicon carbide, and zirconia.”—Geoffrey A. Landis, “Small Laser-Propelled Interstellar Probe,” presented at the 46th International Astronautical Federation Congress, Oslo, Norway, October 1995 (IAA-95-IAA.4.1.102).Google Scholar
  27. p.135
    “it would heat to higher levels in the beam than he had originally calculated.”—Geoffrey A. Landis “Dielectric Films for Solar and Laser-Pushed Lightsails,” CP5o4, Space Technology and Applications International Forum-2000, edited by M. S. EI-Genk (American Institute of Physics, 2000).Google Scholar
  28. p.135
    “A bubble is transparent but you can see the colors”—Landis interview, April 3, 2003.Google Scholar
  29. p.135
    “Robert Forward had proposed using diamond laser sails as early as 1986.”—Robert L. Forward, “Laser Weapon Target Practice with Gee-Whiz Targets,” Proc. SDIO/DARPA Workshop on Laser Propulsion, July 7–18,1986, ed. Jordin Kare. Lawrence Livermore National Laboratory CONF-86o778, vol. 2 (1987): 41-44.Google Scholar
  30. p.136
    “as thin as 5oo carbon atoms.”—From “The World’s Smoothest Diamond Films Pave the Path for Microscopic Motors,” Frontiers 2004 Argonne National Laboratory. Available online at: http://www.anl.gov/OPA/frontiers2oor/b4excell.html.Google Scholar
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    “a future lightsail is thus well within the realm of the possible”—Paul W. May, “Diamond Thin Films: a 21st Century Material.” Philosophical Transactions of the Royal Society of London, Series A (2000): 473-95.Google Scholar
  32. p.136
    “it would use microwave power to return images from the encounter.”—Robert L. Forward, “Starwisp: An Ultra-Light Interstellar Probe,” J. Spacecraft 22 (1985b): 345-5o.Google Scholar
  33. p.136
    “the effect of an intense microwave beam on the materials from which the spacecraft was made.” —Geoffrey Landis, “Advanced Solar-and Laser-Pushed Lightsail Concepts,” Final Report for NASA Institute for Advanced Concepts, May 31,1999. Available online at http://www.niac.usra.edu.Google Scholar
  34. p.136
    “It would absorb all the power and vanish.”—Landis interview, April 3, 2003.Google Scholar
  35. p.137
    “the technology to demonstrate the use of microwaves for propulsion is available today.”—Geoffrey A. Landis, “Microwave-Pushed Sails for Interstellar Travel,” presentation to the loth Advanced Propulsion Workshop, Huntsville, Alabama, April 5–8, 1999.Google Scholar
  36. p.137
    “with interesting side effects that require further study.”—In particular, “desorption,” the out-gassing of materials in the sail as its temperature rises, can produce its own thrust, an effect not originally anticipated when Benford began his work.Google Scholar
  37. p.137
    “beamed energy clearly works, i.e., needs no new physics, and has the most potential for near-term development.” —Microwave Sciences, Inc., “Final Report: Laboratory Demonstration of Microwave Beamed Power Propulsion,” Project Number R-700–200z58–30025 (for Ohio Aerospace Institute).Google Scholar
  38. p.138
    “the ramjet was not feasible.” —As explained in Robert Zubrin’s Enter Space: Creating a Spacefaring Civilization (New York: Tarcher/Putnam, 1999).Google Scholar
  39. p. 138
    “the magsail can be generated from within the spacecraft, eliminating spars or supporting materials.”— D. G. Andrews and R. M. Zubrin, “Magnetic Sails and Interstellar Travel,” International Astronautical Federation Paper IAF-88–5533 Bangalore, India, October 1988.Google Scholar
  40. p.139
    “Winglee thinks velocities of 5o to 8o kilometers (31 to 5o miles) per second are possible.”—Robert Winglee, “Mini-Magnetospheric Plasma Propulsion, M2P2,” NIAC Award No. 07600-o32. Final Report, November 2001.Google Scholar
  41. p. 140
    “We’re figuring out how to do this ourselves.”—Telephone interview with Robert Winglee, January 15, 2003.Google Scholar
  42. p.141
    “What M2P2 can do in the solar system, we should be able to modify for interstellar work.”—Landis interview, April 3, 2003.Google Scholar
  43. p.141
    “nuclear bombs set off behind the vehicle to create the plasma that would drive a magnetic sail.”—Dana Andrews and Robert Zubrin, “Nuclear Device-Pushed Magnetic Sails (MagOrion),” American Institute of Aeronautics and Astronautics Paper 97-3072 33rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, Seattle, Washington, 1997.Google Scholar
  44. p.142
    “before being positioned into the path of a particle beam.”—Gregory Matloff, “Robosloth: A Slow Interstellar Thin-Film Robot,” Journal of the British Interplanetary Society 49 (1996): 33-36. Also see his discussion of particle-beam propulsion in his book Deep Space Probes (Chichester, U.K.: Praxis Publishing, z000), pp. 97–98.Google Scholar
  45. p.142
    “vast electromagnetic launchers some tens of thousands of kilometers long.”— Clifford Singer, “Interstellar Propulsion Using a Pellet Stream for Momentum Transfer,” Journal of the British Interplanetary Society 33 (March 1980): 107–115.Google Scholar
  46. p.143
    “such as lunar regolith or asteroids.” —Nordley had written up these ideas in “Beamriders,” a science article for Analog Science Fiction and Fact, vol.119, no. 6 (July/August, 1999), and had discussed an earlier version in “Relativistic Particle Beams for Interstellar Propulsion,” Journal of the British Interplanetary Society 46, no. 4 (1993), pp. 145-5o. He added the self-steering pellet concept in a presentation at the 4th NASA advanced propulsion workshop at JPL in 1993 and extended it in a paper called “Interstellar Propulsion by Self-Steering Momentum Transfer Particles,” presented at the 52nd International Astronautical Congress in Toulouse, France (IAA.4.1.05), October 2001.Google Scholar
  47. p.144
    “an efficient design, more efficient than any lightsail.” —Telephone interview with Gerald Nordley, May 12, 2003.Google Scholar
  48. p.145
    “I started doing the calculations and realized that this made sense as a propulsion system.”—Telephone interview with Jordin Kare, January 7, 2003.Google Scholar
  49. p.146
    “the spacecraft is not coupled to the sails but driven by them.” —Jordin T. Kare, “SailBeam: Space Propulsion by Macroscopic Sail-Type Projectiles,” CP552, Space Technology and Applications International Forum-2001, edited by M. S. El-Genk (American Institute of Physics, 2001).Google Scholar
  50. p.146
    “NASA’s Institute for Advanced Concepts.” —Jordin T. Kare, “HighAcceleration Micro-Scale Laser Sails for Interstellar Propulsion,” Final Report, NIAC Research Grant #07600–070, revised February 15, 2002. p.146: “I love showing that slide”—Jordin Kare interview, January 7, 2003.Google Scholar
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    “So it probably scales up better than most other schemes”— Ibid.Google Scholar
  52. p.149
    “Galactic Matter and Interstellar Spaceflight.”— Robert W. Bussard, “Galactic Matter and Interstellar Spaceflight.” Astronautica Acta 6 (1960):179-94.Google Scholar
  53. p.149
    “given our current inability to drive a fusion reactor with them.”—These numbers are drawn from R. H. Frisbee and S. D. Leifer, “Evolution of Propulsion Options for Interstellar Missions,” a paper presented to the 34th Joint Propulsion Conference & Exhibit, July 13–18, Cleveland, Ohio. AIAA paper 98–3403, as cited in Landis, “The Ultimate Exploration.”Google Scholar
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    “some 4,000 kilometers in diameter, about the distance from Atlanta to San Francisco.”—Carl Sagan, “Direct Contact among Galactic Civilizations by Relativistic Spaceflight,” Planetary and Space Science n (1963): 485–98.Google Scholar
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    “a novel by Poul Anderson called Tau Zero that made them ponder the seemingly impossible.” —Poul Anderson, Tau Zero (New York: Doubleday, 1970).Google Scholar
  56. p.150
    “If there was any single book that turned me on to actually engineering interstellar flight,” Jordin Kare told me, “it was Tau Zero.” —Jordin Kare interview, January 7, 2003Google Scholar
  57. p.151
    “danced always on the same edge of disaster.. ”—Ibid., 43.Google Scholar
  58. p.152
    “ramjet-propelled spacecraft became available to a much broader audience.”—Carl Sagan and I. S. Shklovskii, Intelligent Life in the Universe (San Francisco: Holden-Day, 1966).Google Scholar
  59. p.152
    “to accelerate the hydrogen into an exhaust stream.”—Alan Bond, “An Analysis of the Potential Performance of the Ram Augmented Interstellar Rocket.” journal of the British Interplanetary Society 27 (1974): 674–685.Google Scholar
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    “fuel provided by the ramjet’s electromagnetic scoop.”— See Gregory Matloff and Eugene Mallove, “Interstellar Flight: Aspects of Beamed Electric Propulsion,” International Electric Propulsion Conference proceedings (A89–47426, 21–20), Garmisch-Partenkirchen, Federal Republic of Germany, Oct. 3–6,1988 (Bonn: Deutsche Gesellschaft für Luft-, and Raumfahrt, 1988), 499–501.Google Scholar
  61. p. 15
    : “you’re trying to add energy to an already energetic mass stream.”—Gerald Nordley interview, May 12, 2003.Google Scholar

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© Springer Science+Business Media New York 2004

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  • Paul Gilster

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